Is it at all possible for me to be pregnant?

Me and my boyfriend last had sex December 6th.. a day before my IUD insertion (pregnancy test on the 6th at the gynecologist was negative) we haven’t had sex since but I’ve been gaining some weight and feeling little twitches in my uterus.. am I just paranoid? I’ve been bleeding too so I don’t think the uterine lining could shed with a baby in it right? We did use protection
Is it at all possible for me to be pregnant?
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